Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Net realized investment gains	$ (20,179)	$ 4,055	$ 4,947
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	785,778	779,966	683,662
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(54,167)	(54,253)	(31,229)
Consolidated Property and Casualty Insurance Entity
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Deferred Policy Acquisition Costs	92,796	88,102	93,362
Reserves for Unpaid Claims and Claim Adjustment Expenses	1,312,483	1,224,183	1,123,896
Unearned Premiums	492,918	465,391	443,802
Earned Premiums	1,037,451	997,492	936,131
Net realized investment gains	(20,179)	4,055	4,947
Net Investment Income	52,894	51,190	55,284
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	785,778	779,966	683,662
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(54,167)	(54,253)	(31,229)
Amortization of Deferred Policy Acquisition Costs	206,232	207,746	202,892
Paid Claims and Claim Adjustment Expenses	640,534	625,503	537,573
Premiums Written	$ 1,061,664	$ 1,019,113	$ 964,970